This initiative is referred to as "the mobile surge" in some of the documents. The surveillance tapped apps of popular services like Facebook, Flickr, LinkedIn and Twitter for user information such as address books, buddy lists and phone logs. The reports say Google Maps was of particular interest to the agencies because of all the geo-location data users put into it.

The documents also say the agencies are capable of tracking similar information from newer apps like "Angry Birds," which work with third-party advertising companies. Those companies create profiles that contain valuable personal data that can then be grabbed by the NSA.

According to the news agencies, the profiles contain information that identifies the phone as well as users' age, sex and location. Some profiles contain users' ethnicity, marital status and even sexual orientation.

It's unclear whether the NSA and the British agency track newer apps. It's also not known how many users have been tracked through "the mobile surge," but the documents say the NSA and its British counterpart had more information than they even knew what to do with. Getting through one month of the smartphone data collected by the NSA required 120 computers, according to the documents.

In response to the reports, the NSA said it does not track American users or innocent foreign citizens. The British agency said all its activities comply with British law. Meanwhile, Rovio, the maker of Angry Birds, said it was not aware of the use of any intelligence programs. The company also said it has no involvement with either agency.

According to the documents, "the mobile surge" has had success, helping to stop a bomb plot by Al Qaeda that was planned for Germany in 2007. It also lead to the arrests of Mexican drug cartel members suspected of murdering an employee of the U.S. Consulate in Mexico.